Tormentil

Tormentil is a low, clump-forming perennial of the rose family, Rosaceae, with a single yellow four-petalled flower on a long stalk, found on acid soils across Europe and western Asia. Wikipedia lists septfoil and erect cinquefoil among its names and says its thick rhizomatous root is unusually high in tannin, is used in herbal medicine as an astringent, and flavours a bitter Bavarian liqueur called Blutwurz. Grieve names it Potentilla Tormentilla and gives root and herb as the parts used, with a long list of country names. The American Herbal Products Association covers the rhizome under Potentilla erecta, with Potentilla tormentilla as a synonym, and records that cinquefoil may cause gastric discomfort in sensitive people, set out in the safety notes. This entry has no magical correspondences, because neither Cunningham nor Kynes has a tormentil entry.